Operating mechanism for manually actuated switches



ay 1967 w. A. DE SMIDT OPERATING MECHANISM FOR MANUALLY ACTUATED SWITCHES 2 Sheets-$heet 1 Filed Feb. 1, 1966 FIG. 2.

United States Patent 3,320,395 OPERATING MECHANISM FOR MANUALLY ACTUATED SWITCHES Woodrow A. De Smidt, Whitefish Bay, Wis, assignor to Allen-Bradley Company, Milwaukee, Wis., a corporation of Wisconsin Filed Feb. 1, 1966, Ser. No. 524,153 11 Claims. (Cl. 200168) This invention relates to an enclosed electrical switching station and it resides more specifically in a combination of an electrical switch assembly contained within an enclosed housing and a manual actuating means for controlling operation of the switch assembly from a position external to the housing. The combination comprises an operating shaft projecting from the interior of the housing to the exterior thereof with the exterior portion of the shaft engaging a manually actuatable lever. Within the housing, the station includes means for converting the rotary motion of the operating shaft to linear reciprocal motion, which means controls operation of the switch assembly. The invention further teaches that the combination may include means for absorbing abnormally large forces in the actuating means without the abnormal forces being transmitted to the switch assembly and also means for minimizing overtravel.

Electrical switches such as push button switches are frequently used at switching stations to start and stop electrical machinery. Frequently these stations are located at hazardous, explosive locations and the switches must be enclosed within housings to elfectively seal the electrical switch contacts from the ambient surroundings. Such hazardous surroundings include those encountered in grain elevators, fiour mills, filling stations, dry cleaning establishments, petroleum refineries, distilleries, etc. For satisfactory protection in such locations, care must be exercised in providing dust, gas or liquid tight switch compartments. Besides use in hazardous locations, there are other switch applications requiring watertight housings or housings that exclude oil products, dirt and dust to a greater degree than standard switch enclosures.

Heretofore enclosed switches meeting these requirements have had operating shafts projecting from within the housing to the exterior with external manually operated actuators. One type of such enclosure is illustrated in United States Patent 2,702,845 granted to Woodrow A. De Smidt on Feb. 22, 1955, and assigned to the assignee of the present invention. The present invention is an improved version of the patented version. The present design converts the rotary motion of the external shaft to reciprocal internal motion for actuating the switch assembly. This permits the housing to be smaller in dimensions. To accomplish the conversion, there is an internal arm attached to the operating shaft such that the internal arm rotates concurrently with the external arm. Engaging opposing ends of the internal arm are a pair of plungers which reciprocate linearly along an axis perpendicular to the axis of the rotating shaft. As the internal arm rotates, it engages a plunge-r and applies a force component parallel to the direction of movement of the plunger. At the same time, the arm slides across the plunger in a plane normal to the movement of the plunger, thereby changing the effective moment arm.

To absorb abnormal forces applied to the external manual actuator, the internal arm has an enlarged aperture intermediate the distal ends. A pin member, with an absorbing spring encircling its shank, protrudes through the oblong aperture and engages the rotating shaft, with the spring urging the internal arm against the rotating shaft. When the plunger assumes its bottoming position, a continued abnormal force is absorbed in the absorbing 3,320,395 Patented May 16, 1967 spring and the enlarged aperture of the internal arm permits the arm to slide about the shank of the pin member and across the plunger in a plane substantially normal to the direction of the reciprocal motion.

The present invention may be further designed such that overtravel of the actuating arm is minimized and absorbed by the plunger assembly. The plungers may be designed such that they resist the rotational movement of the internal actuating arm. When an arm, in returning to its normal position after engaging a plunger travels beyond the normal operating point, the opposing plunger tends to retard further rotation. The end of the plunger and associated switch may be spaced such that the plunger must travel a minimum distance before engaging the switch. The spacing may be selected so that overtravel alone will not cause the plunger to exceed the spaced distance. Thus, the overtravel is substantially absorbed by the plunger assembly without the switch buttons being engaged.

The foregoing features and advantages of the invention will appear in the description to follow. Reference is made in the description to the accompanying drawings which form a part hereof and in which there is shown by way of illustration and not of limitation one specific form in which the invention may be embodied.

In the drawings:

FIG. 1 is a perspective view, with parts broken away and in section, of a switch housing enclosing a pushbutton switch assembly and having an actuating means constructed in accordance with this invention.

FIG. 2 is a sectional view taken along the sectional line 22 of FIG. 1.

FIG. 3 is an exploded view of the operating shaft, the internal arm, the absorbing spring and the'fastener of the actuating means of FIG. 1.

FIG. 4 is a perspective View of the standard push button switch assembly and the associated plunger assembly of the housing of FIG. 1.

FIG. 5 is a longitudinal sectional view of the housing of FIG. 1 with the assembly in a normal activated position.

FIG. 6 is a longitudinal sectional view of the housing of FIG. 1 with the actuating means in an abnormal activated position due to abnormal forces applied to the external arm.

Referring now to the drawings, there is shown in FIGS. 1 and 2 an enclosed electrical switch housing referred to by the general reference character 1. In FIGS. 1 and 2' the switch assembly is shown resting on a horizontal plane and in a neutral non-activated position. The walls of the switch housing 1 define an internal spacing including 1 a rectangular-shaped base cavity referred to by the gen' eral reference character 2. The housing 1 further includes a cover assembly referred to by the general reference character 3, and having a raised boss portion 3a. The base cavity 2 and cover assembly 3 may comprise an aluminum alloy die casting structure. The base cavity 2 carries a pipe tap 4 having internal threads for attachment to a metallic conduit (not shown) surrounding electrical lead wires. The base cavity 2 further carries a plurality of internal ribs 5 having threaded apertures 6 for receiving a plurality of threaded fasteners 7 securing the cover assembly 3 to the base cavity 2. Intermediate the cover assembly 3 and base cavity 2 is a gasket 8 providing means for sealing the internal operating components against a contaminating atmosphere.

In the illustrated housing 1, the switch actuating assembly is primarily secured to the cover assembly 3; The assembly 3 includes an external actuating arm referred to by the general reference character 10, which in FIG. 1 is partially broken away. The actuating arm 10 includes a shank 11 having a substantial triangular shape with a relatively flat top surface and a bottom surface inclined from a central opening 12 towards its opposite ends. The opposing ends of the shank 11 provide a pair of serrated finger pads 13 extending substantially normal to the longitudinal axis of the shank 11 and spaced above the cover assembly 3. At the aperture 12, the actuating arm engages a rotatable operating shaft 14, one end of which extends externally through a sidewall of a raised boss portion 3a of the cover 3. The other end of the shaft 14 is contained internally within a cavity 15 of the boss portion 3a of the cover assembly 3. The shaft 14 is rotatably supported within the cover assembly 3 by an annular bore 16 (see FIG. 2) disposed transversely of the boss 3a and intercepting the cavity 15. The shank 11 of the actuating arm 10 is fastened to the external portion of the shaft 14 by means of a set screw 17, the threads of which coincide with the threaded aperture 18 of the operating shaft 14. Thus, the external actuating arm 10 responds to alternative pressure applied to the finger pads 13. The arm 10 rotates about the axis of the shaft 14 and the exterior walls of the boss 3a in a direction dependent upon which of the pads 13 is manually depressed. This action serves to rotate the operating shaft 14 in a corresponding direction about its longitudinal axis. Around the base of the boss 3a is a flange 19 part of which is beneath the opposite ends of the external actuating arm 10. The actuating arm 10 bottoms on the flange 19 when the arm 10 is rotated a suflicient amount.

Intermediate the ends of the shaft 14 and within the cavity 15 is an internal actuating plate arm 20 engaging the shaft 14. The actuating arm 20 is disposed normal to the rotational axis of the shaft 14 and is secured thereto by means of a resilient member in the form of a spiral compression spring 21 and a fastener pin 22 threaded at an end 23 to engage a threaded transverse aperture 24 in the 'shaft 14. The spring 21 and pin 22 are illustrated in the exploded view of FIG. 3. As illustrated in FIG. 3, the actuating arm 20 has a transverse rectangular cross section and is provided with a centrally disposed oblong aperture 25. The major axis of the oblong aperture 25 is parallel to the longitudinal axis of the arm 20. The pin 22 has a shank portion 26 of cross-sectional dimensions larger than the threaded portion but slightly less than the internal diameter of the compression spring 21 such that the spring 21 can be slid over and encircle the shank 26. The external diameter of the spring 21 is larger than the minor axis of the oblong aperture 25 such that the compression spring 21 will provide a biasing pressure against the lower surface of the arm 20. To receive the arm 20, the shaft 14 is provided with a flat bottomed seat 27 to coincide with the flat surface of the arm 20 at the point the aperture 25 aligns with the aperture 24. The present embodiment is designed such that when the shaft 14, the actuating arm 20, the compression spring 21 and the pin 22 are secured in place, the arm 20 is positioned flush against the bottom of the seat 27 of the shaft 14, and the spring 21 surrounds the shank 26 urging the arm 20 against the shaft 14. At the same time, when a force parallel to the longitudinal axis of the arm 20 is applied to the arm 20, and which force is greater than the frictional longitudinal force resulting from the compression spring 21, the arm 20 will be permitted to slide along its longitudinal axis normal to the axis of the pin 22. The arm 20 further carries a pair of angled wings 28 disposed oppositely of the aperture 25.

FIGURE 4 illustrates a standard push-button switch assembly designated by the general reference character 30. The switch assembly 30 has a pair of contact terminals 31 and '32 for respectively receiving a pair of electrical wires (not shown). The switch assembly 30 further carries a pair of push-buttons 33 and 34 one of which may be used to alternatively close and open an electrical circuit between the terminals 31 and 32.

Mounted upon the switch assembly 30 is a plunger assembly designated by the general reference character 40. The plunger assembly 40 is designed to convert the arcuate motion of the internal actuating arm 20 to reciprocal linear motion for operating the push-buttons 33 and 34. The switch assembly 30 is connected to the plunger assembly 40 by means of a pair of fasteners 41 and 42 which engage a supporting plate 43. The supporting plate 43 is pierced to provide a pair of rectangular apertures 44 respectively receiving a pair of substantially Y-shaped, laterally spaced plungers 46. Each of the plungers 46 comprises an upstanding post 48 received by the aperture 44, a pair of upraised arms 49, and a crossbar 50 intersecting the post 48 and arms 49. The free end portion of each of the posts 48 is located at the opposite side of the supporting plate 43 and are bent at an angle to form a tab 51. The tab 51 is formed to be substantially perpendicular to the post 48 and the crossbar 50. The tabs 51 are respectively positioned to actuate the push-buttons 33 and 34. Supporting each plunger 46 in a vertical position relative to FIG. 4 and biasing its tab 51 away from the respective push-buttons 33 and 34 is a resilient member in the form of a spiral biasing spring 52 disposed between the crossbar 50 and the support plate 43. The tabs 51 serve a dual purpose, one purpose of which is to engage an associated push-button when the associated plunger 46 is in a depressed position and secondly, act as a stop for preventing the plunger 46 from escaping the associated aperture 44 due to the force of the associated spring 52 when in a neutral position. It may be noted at this point that the spacing between plungers 46 is less than the longitudinal length of the internal actuating arm 20. Also, the length of the crossbars 50 joining the arms 49 is slightly greater than the width of the internal actuating arm 20 such that the opposing ends 28 of the actuating arm 20 may engage the plungers 46 and be embraced by the arms 49.

The switch assembly 30 and the plunger assembly 40 are supported by the cover assembly 3 by means of a pair of spaced fasteners 60 which extend through apertures 61 of the cover plate 3 and the apertures 62 of the supporting plate 43 (see FIGS. 5 and 6). Assuming a normal or neutral position of the actuating arm 10, as shown in FIG. 1, the plungers 46 will be biased away from the push-buttons 33 and 34 by the force of each of the biasing springs 52.

Upon manual depression of one of the finger pads 13, (the right pad as illustrated in FIG. 5) the external actuating arm 10 will be rotated externally of the hollow boss 3a and the rotatable operating shaft 14. The internal actuating arm 20 will be rotated correspondingly.

The rotation of the shaft 14 is illustrated by an arcuate double arrow 63 in FIGS. 5 and 6. If the external pressure applied to the right hand finger pad 13, as indicated by an arrow 64, is suflicient to overcome the force resulting in part from friction and the biasing spring 52, the internal arm 20 forces the associated plunger towards the switch assembly 30, and the right hand tab 51 will engage the associated push-button, which in FIG. 5 is push-button 34. The reciprocal linear motion of the plungers 46 is illustrated by the straight double arrows 65.

Upon removal of the pressure applied to the finger pad 13, the expansion force of the biasing spring 52 acting against the crossbar 50 of the respective plunger 46 causes the plunger 46, the internal actuating arm 20 and the external actuating arm 10 to return towards their neutral positions. Upon return of the actuating arm 20 towards the neutral position, it will normally have a tendency to overtravel? and go beyond the neutral point due to the force of the spring 52. However, in the present design overtravel is minimized. When the actuating arm 20 reaches the neutral point and attempts to go beyond in the opposite direction, a counteracting force is applied by the opposing biasing spring 52 thereby minimizing the overtravel. Though there may be slight overtravel and movement of the opposing plunger 46, since the tabs- 51 are spaced from the associated push-button,-t-he move-- meat will not be sufiicient to engage the push-button, assuming care is taken in selecting the springs 52 and the spacing between the tabs 51 and their associated pushbuttons. Minimizing overtravel minimizes accidental actuation of the opposing push-button.

FIG. 5 illustrates switch actuation during normal operation of the sWitch mechanism. However, it is not uncommon for abnormal forces to be applied to the externally actuated arm. These forces may result from an overenthusiastic operator or a falling object coming into contact with the external actuating arm 10. The situation of an excessive force being applied to a finger pad 13 is demonstrated in FIG. 6 by the two arrows 64. The present design permits the application of such abnormal forces without having said forces absorbed by the switch assembly 30 itself unless the housing 1 is destroyed. When an abnormally large force is applied to a finger pad 13, the external actuating arm 10 has a tendency to rotate until it bottoms on the exterior flange 19 of the cover assembly 3 as illustrated by the right hand pad 13 of FIG. 6. With the exterior arm 10 rotating to this extreme position, the internal plate 20 likewise attempts to follow. In viewing and comparing the position of the right hand finger pad 13 in FIGS. 5 and 6, it will be noted that the distance travelled in FIG. 6 is substantially greater than that of FIG. 5. However, the distance travelled by the internal arm 20 is approximately the same in both instances. This results from the feature that when the tension on the bias spring 52 in conjunction with the restraining force of the actuated push-button reaches a certain point, it exceeds the counteracting force of the compression spring 21 surrounding the pin 22. The force of the spring 21 varies according to the position of the internal arm 20. At the point the force of the spring 21 is exceeded, and because of the oblong configuration of the aperture 25 of the arm 20, the actuating plate 20 will shift away from the plunger to thereby shorten the moment arm. Accordingly, the associated plunger 46 does not advance beyond the point which would otherwise cause excessive and detrimental forces to be applied to the push-button switch assembly 39. When the abnormal force is released from the finger pad 13, the force of the biasing spring 52 will return the actuating arm 20 towards its neutral position. It may be noted that when the plunger ,46 engages its respective push-button in FIGS. 5 and 6, that the end 28 of the arm 20 is substantially normal to the upraised arm 49 and crossbar 50 of the associated plunger 46. Further, it may be noted that the bottom surface of the triangular shaped shank 11 of the external actuating arm 10 is designed to bottom on the flange 19 of the housing 1 concurrently with the bottoming of the associated finger pad 13. Thus, the abnormal forces are distributed over a greater portion of the arm 10 and housing 1.

Referring more specifically to the cavity 15 of the cover plate assembly 3, it will be noted that it is grooved at to receive the free ends of the upraised arms 49 of a respective plunger 46. The slots 70 guide the reciprocal linear movement of the plungers 46. It may be noted from FIG. 2 that when the actuating arm 10 is. in its neutral position, the upraised arms 49 bottom at the top of the slots 70 such that when in the neutral position there is little, if any, pressure applied to the internal actuating arm 20.

The cover assembly 3 is preferably provided with external ribs flanking the finger pads 13 (see FIG. 1). These ribs serve to protect the pads 13 from receiving blows from large objects. The ribs 75 along with the exterior walls of the cavity 15 further serve as guides for an operator feeling for the finger pad when his attention may in part be diverted to other portions of the particular machinery under control of the switch. The embodiment further illustrates that the ribs 75 may have a pair of aligned circular apertures 76 coinciding with one finger seat 13. These apertures 76 permit a padlock or other similar device to be placed through the holes to maintain an associated seat 13 in a depressed'position. Normally the apertures 76 coincide withe the stop or off finger seat 13. The present embodiment further features an O- ring 77 disposed about the shaft 14 (see FIGS. 2 and 3). The O-ring 77 has an inner dimension slightly less than the diameter of the shaft 14 thereby permitting a snug fit. The outer dimensions of the O-ring 77 are slightly greater than the interior diameter of the aperture through which the shaft 14 protrudes. The O-ring 77 discourages gases, moisture or foreign objects from entering the cavity 15. The O-ring 77 further creates a drag. The drag aids the springs 52 in dissipating the inertial energy of the actuating arms 10 and 20 when pressure is released from the finger pads 13 and minimizes overtravel.

In the illustrated embodiment, the aperture 25 of the actuating arm 20 has been shown (FIG. 3) and discussed as oblong. However, the invention is not so limited. To realize the shifting feature of the arm 20 when abnormal forces are applied it is only necessary that the dimensions of the aperture parallel to the longitudinal axis of the arm exceed the dimensions of that part of the shank 26 extending through the aperture. For example, the aperture may be circular with the diameter greater than the diameter of the shank 26 but less than the diameter of the spring 21.

, I claim:

1. An enclosed electrical switching station comprising, in combination:

a housing, the walls of which define an internal cavity therein and a shaft receiving aperture therethrough; an electrical switch assembly supported in said housing cavity; a rotatable operating shaft having a portion extending internally of said housing through said apertrue; an external actuating arm engaged with and arranged to operate said shaft; 7 i a second actuating arm residing in said housing cavity and operably engaging the internal portion of said shaft, said second actuating arm positioned substantially normal to the rotational axis of said shaft;

overtravel takeup means interposed between said second actuating arm and said shaft permitting said second actuating arm to be laterally movable relative to the axis of said shaft; j

. a reciprocally, linearly movable plunger supported in said housing cavity independently of said second actuating arm and said switch assembly, and adapted to actuate said switch assembly, said plungerslidably engaging said second actuating arm at a point spacedfrom said shaft;

whereby rotational movement of said shaft will be transmitted to said plunger to provide linear motion of said plunger.

2. An enclosed electrical switching station in accordance with claim 1 in which the second actuating arm engages the shaft at a point intermediate the opposing longitudinal ends of the second actuating arm, the second actuating arm having an aperture coinciding with the point at which the second actuating arm engages the shaft, a pin member protruding through said aperture and engaging the shaft, said pin member having a shank of cross-section dimensions less than the size of the aperture permitting the second actuating arm to slide about said shank, a resilient member surrounding said pin member and without said aperture, said resilient member urging the second actuating arm towards the shaft.

3. An enclosed electrical switching station comprising,

in combination: Y

a housing, the Walls of which define an internal cavity therein and a shaft receiving aperture therethrough;

an electrical switch assembly supported in said housing cavity;

a rotatable operating shaft having a portion extending internally of said housing through said aperture;

an external actuating arm engaged with and arranged to operate said shaft;

a second actuating arm residing in said housing cavity and operably engaging the rotatable operating shaft at a point intermediate the opposing longitudinal end points of the second actuating arm and extending substantially normal to the rotational axis of said shaft;

a pair of plungers independently supported within the housing for independent linear motion substantially normal to the axis of the operating shaft and substantially normal to the longitudinal axis of the second actuating arm, the opposing longitudinal ends of the second actuating arm each slidably engaging one of the plungers, whereby the plungers are alternatively urged towards the switch assembly depending on the rotational direction of the second actuating arm;

whereby rotational movement of said shaft will be transmitted to said plungers to provide linear motion to said plungers.

4. An enclosed electrical switching station in accordance with claim 3 including resilient means biasing the plungers in a neutral position away from said switch assembly when the second actuating arm is in an unactuated neutral position, the resilient means further resisisting movement of the plungers towards said switch assembly when the second actuating arm rotates beyond the neutral position towards the switch assembly.

5. An enclosed electrical switching station in accordance with claim 1 in which the second actuating arm engages the shaft at a point intermediate the opposing longitudinal end points of the second actuating arm, the second actuating arm having an aperture coinciding with the point at which the second actuating arm engages the shaft, a pin member protruding through said aperture and engaging the shaft, said pin member having a shank of crosssection dimensions less than the size of the aperture permitting the second actuating arm to slide about said shaft, a resilient member surrounding said pin memher and without said aperture, said resilient member urging the second actuating arm towards the shaft; and

including resilient means biasing the plunger in a neutral position away from said switch assembly when the second actuating arm is in an unactuated neutral position, the resilient means further resisting movement of the plunger towards said switch assembly when the second actuating arm rotates beyond the neutral position towards the switch assembly.

6. An enclosed electrical switching station in accordance with claim 2, and including a pair of plungers independently supported within the housing for independent linear motion substantially normal to the axis of the shaft and substantially normal to the longitudinal axis of the second actuating arm, opposing longitudinal ends of the second actuating arm each slidably engaging one of the plungers, whereby the plungers are alternatively urged towards the switch assembly depending on the rotational direction of the second actuating arm; and

resilient means biasing the plungers in a neutral position away from said switch assembly when the second actuating arm is in an unactuated neutral position, the resilient means further resisting movement of the plungers towards said switch assembly when the second actuating arm rotates beyond the neutral position towards the switch assembly.

7. An enclosed electrical switching station in accordance with claim '6, in which the first actuating arm has a shank portion and a pair of finger pads at opposite ends, each of said pads extending backward to overlie a wall surface of the housing, said shank portion engaging the external portion of the shaft at a point intermediate said pads such that when pressure is applied to one pad the shaft rotates in one direction and when pressure is applied to the other seat the shaft rotates in the opposite direction.

8. An enclosed electrical switching station in accordance with claim 7, in which said internal cavity of the housing includes a first and 9. An enclosed electrical switching station in accordance with claim 8 including an O-ring surrounding the shaft, the O-ring concurrently engaging the shaft and the interior wall surfaces of the shaft receiving aperture, whereby the O-ring dissipates inertial energy developed by rotation of the shaft.

10. An enclosed electrical switching station in accord ance with claim 6 in which the plungers have a pair of upraised arms and an upstanding post joined in a substantial Y-shaped configuration with the arms branching out from one end of the post, said arms of each plunger embracing the respective ends of the second actuating arm; and in which the resilient means comprise a pair of biasing springs,

one biasing spring engaging an arm member of one plunger and the other biasing spring engaging an arm member of the other plunger, said biasing springs urging their respective plunger away from said switch assembly.

11. An enclosed electrical switching station in accord ance with claim 10, including a support plate positioned above said switch assembly, the support plate pierced by a pair of apertures slightly greater than the cross-section dimensions of the post portion of the Y-shaped plungers, and in which said post portion of one plunger extends through one aperture and said post portion of the other plunger extends through the other aperture, each post carrying a tab on the opposite end which tab is substantially normal to the axis of the respective post; and

pair of biasing springs, one biasing spring concurrently engaging the support plate and an arm member of one plunger, and the other biasing spring concurrently engaging the support plate and an arm member of the other plunger.

References Cited by the Examiner UNITED STATES PATENTS 10/1965 De Smidt 200-168 ROBERT K. SCHAEFER, Primary Examiner.

H. O. JONES, Assistant Examiner. 

1. AN ENCLOSED ELECTRICAL SWITCHING STATION COMPRISING, IN COMBINATION: A HOUSING, THE WALLS OF WHICH DEFINE AN INTERNAL CAVITY THEREIN AND A SHAFT RECEIVING APERTURE THERETHROUGH; AN ELECTRICAL SWITCH ASSEMBLY SUPPORTED IN SAID HOUSING CAVITY; A ROTATABLE OPERATING SHAFT HAVING A PORTION EXTENDING INTERNALLY OF SAID HOUSING THROUGH SAID APERTURE; AN EXTERNAL ACTUATING ARM ENGAGED WITH AND ARRANGED TO OPERATE SAID SHAFT; A SECOND ACTUATING ARM RESIDING IN SAID HOUSING CAVITY AND OPERABLY ENGAGING THE INTERNAL PORTION OF SAID SHAFT, SAID SECOND ACTUATING ARM POSITIONED SUBSTANTIALLY NORMAL TO THE ROTATIONAL AXIS OF SAID SHIFT; OVERTRAVEL TAKEUP MEANS INTERPOSED BETWEEN SAID SECOND ACTUATING ARM AND SAID SHAFT PERMITTING SAID SECOND ACTUATING ARM TO BE LATERALLY MOVABLE RELATIVE TO THE AXIS OF SAID SHAFT; A RECIPROCALLY, LINEARLY MOVABLE PLUNGER SUPPORTED IN SAID HOUSING CAVITY INDEPENDENTLY OF SAID SECOND ACTUATING ARM AND SAID SWITCH ASSEMBLY, AND ADAPTED TO ACTUATE SAID SWITCH ASSEMBLY, SAID PLUNGER SLIDABLY ENGAGING SAID SECOND ACTUATING ARM AT A POINT SPACED FROM SAID SHAFT; WHEREBY ROTATIONAL MOVEMENT OF SAID SHAFT WILL BE TRANSMITTED TO SAID PLUNGER TO PROVIDE LINEAR MOTION OF SAID PLUNGER. 